import java.util.Scanner;
import java.util.TreeMap;

public class HJ8 {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        while(sc.hasNext()){
            int lines = sc.nextInt();//行数
            TreeMap<Integer,Integer> map = new TreeMap<Integer,Integer>();

            for(int i=0;i<lines;i++){
                int key = sc.nextInt();//每行的key和value
                int value = sc.nextInt();
                if(map.containsKey(key)){
                    map.put(key, map.get(key) + value);
                }else{
                    map.put(key,value);
                }
            }
            for(Integer key:map.keySet()){
                System.out.println(key + " " + map.get(key));
            }
        }
    }
}
